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Discussion Starter · #1 ·
im building a 383 stroker sbc. bottom end is all forged with 5.7 rods.
heads are aluminum 210 cc runners,64cc,2.05/1.60 valves poted polished 3 angle valve job. 10.3:1cr
750 cfm carb, 4.10 rear,4 speed manual.
i want to go with a lunati cam, probably mech. roller, i was thinking between 2 choices: p/n:lun-60132 243/[email protected] .578/.585 lift
or p/n:lun-60131 237/[email protected] .566/.578 lift.
I want to be able to get up around the 7000RPM range, i was just wondering what cam might be a little more streetable.
Also would a regular solid be ok instead? mech rollers are pricey, but i've herd solid flat tappets are harder to break in, and now having to get special oil with more zinc because of the new gov. standards.
Any help is really appreciated, thanks alot.
p.s. this is going in a 73 camaro if that helps.
 

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What you are talking about is a borderline street driven race car.

Very big heads, very big cam, too small carburetor, and borderline low compression for what components indicate.

You need a cam with a 107* LSA with 1.6 rockers (or 106* with 1.5 rockers) in whichever grind you choose around 242 single pattern. Which actually dictates another full number of compression.

I would not recommend that much cam, but smaller will not give you the top end pull you desire.

I'd lower my rpm sights and go for a 232 single pattern on the above LSA, maybe the 750 carb, ANY carb must be vacuum secondary or air valve secondary is mandatory to be streetable.
I hope those short rods are H beam. You'll need it at 7000 rpm. You will also need an expensive valve train and beehive springs with that flat tappet cam.
 

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Discussion Starter · #3 ·
xntrik said:
What you are talking about is a borderline street driven race car.

Very big heads, very big cam, too small carburetor, and borderline low compression for what components indicate.

You need a cam with a 107* LSA with 1.6 rockers (or 106* with 1.5 rockers) in whichever grind you choose around 242 single pattern. Which actually dictates another full number of compression.

I would not recommend that much cam, but smaller will not give you the top end pull you desire.

I'd lower my rpm sights and go for a 232 single pattern on the above LSA, maybe the 750 carb, ANY carb must be vacuum secondary or air valve secondary is mandatory to be streetable.
I hope those short rods are H beam. You'll need it at 7000 rpm. You will also need an expensive valve train and beehive springs with that flat tappet cam.
yes they are hbeam, mayb ill lower what i wanted for my rpm, will it help if i bring the range down to 6500 or do i need lower? i've herd some people sware by solid falt tappet and some people say no. my machine shop guy said i really should go with a mech roller, but their really expensive...id like to try a solid flat tappet.I'm used hydraulic, but id like to try somethhing different, thanks for your help. I anyone can point me towards a cam(p/n) to start with, that would be great. thanks again.
 

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73camaro said:
yes they are hbeam, mayb ill lower what i wanted for my rpm, will it help if i bring the range down to 6500 or do i need lower? i've herd some people sware by solid falt tappet and some people say no. my machine shop guy said i really should go with a mech roller, but their really expensive...id like to try a solid flat tappet.I'm used hydraulic, but id like to try somethhing different, thanks for your help. I anyone can point me towards a cam(p/n) to start with, that would be great. thanks again.
Seriously, if "expensive" is a big consideration, you need to rethink what you are trying to build. Your drive train and suspension will not be inexpensive either. Remember if you run a TH350 transmission to 7000 rpm that internal drum is turning 17,000 rpm. Boom.

I'd just zip into the online cam catalogs and start browsing. You might get a custom grind. Anytime you get over 6000 rpm you are looking at $1200+ for a reliable and stable valve train. Cam, gears, lifters, pushrods, plates, studs, rockers, springs, retainers, keepers. And 7000 rpm needs to be on Jessel shafts. $$$$$ Flat tappet cams are limited to 300# so beehives are mandatory if you want that much rpm.

Don't forget the fatigue factor. Rockers and springs need periodic replacement unless you want to run them until they fail at 6500 rpm. This is NOT going to be a 50,000 mile no-maintenance engine.

As Grandpa always said, "They usually fail unexpectedly, suddenly, and spectacularly."
 

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Discussion Starter · #5 ·
yea, im gonna go back to the drawing board. I'm not worried about the tranny, i build them for a living..i think the m22 with hardened gears will be ok. The springs annd valve train i will be putting together.
I think im going to be looking at a solid cam arounnd 247/255 525/540 maybe a little bit smaller. thanks alot for your help i really appreciate it
 

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73camaro said:
yea, im gonna go back to the drawing board. I'm not worried about the tranny, i build them for a living..i think the m22 with hardened gears will be ok. The springs annd valve train i will be putting together.
I think im going to be looking at a solid cam arounnd 247/255 525/540 maybe a little bit smaller. thanks alot for your help i really appreciate it
Your biggest consideration will be valve train harmonics and valve train crash..

The cam companies have lots of experience with combinations of springs, rockers, and pushrods, and their recommendations are vital.

I always suggest that a builder get every valve train part from the cam manufacturer.... for the reason outlined above. :thumbup:

You might save a few bucks by doing it yourself,
but what if you have an unexplained torque dip at 4000 rpm, and curve fluctuations,
would it be fuel distribution, fuel atomization, timing, weak ignition, bad scavenging, induction pulsation, or valve train harmonics?
 

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What is the intended use for the car???

I run a solid roller on the street now with no issues. Yes they do require more maintence but are worth it in my opinion. This is NOT my daily driver but does see its fair share of street time.

You will need a good valvetrain but IMO shaft rocker are not needed.

As far as a th350 at 7k.... been doing it for over 5 years on the same transmission...... 10sec et's.
 

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Discussion Starter · #10 ·
Compression will be about 10.5:1 Im going with either a 247 int./255 exh. 0.525 int./0.540 exh. lift with a range from 2800-7000rpm. Or 244 int./252 exh.0.520 int./0.540 exh. 2400-6800rpm. Talked to 2 machine shops, both said those cams would work well. I've been doing more research and i think im going to stick with a solid falt tappet cam thanks alot guys for the help.
 

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Yeah I sometimes forget about comp. the lowest we will build anymore is 12.5 to one and that ain't enough.Seriously most of my builds have been dirt track and I sometimes forget the streetability factor.
 

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i'm a firm believer in less is more in cam selection. i think the latter cam you mentioned, the milder one is a better choice with just over 10 to 1 compression. comp cams list a cam i would think would do well in your motor. it is #280B-8. specs are 242/250 @ .50 .507/.532 on 108*. it says its characteristics are good torque, 10 to 1 compression, 3000+ stall. crane list this cam #114681 its a solid also, 10.5 compression 244/252 @ .50 518/536 lift. 107* i'd use 1.6 rockers with both cams. i have to disagree with whomever it was that said you must run a vacuum secondary carb on the street. ive been running mechanical carbs on street cars for 30 years and frankly think they are MORE streetable. of course you cant put a big double pumper on a stock engine and expect it to work. but on your engine a DP will work well on the street. especially with a stick trans.
 

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Discussion Starter · #14 ·
peteshotrodshop said:
i'm a firm believer in less is more in cam selection. i think the latter cam you mentioned, the milder one is a better choice with just over 10 to 1 compression. comp cams list a cam i would think would do well in your motor. it is #280B-8. specs are 242/250 @ .50 .507/.532 on 108*. it says its characteristics are good torque, 10 to 1 compression, 3000+ stall. crane list this cam #114681 its a solid also, 10.5 compression 244/252 @ .50 518/536 lift. 107* i'd use 1.6 rockers with both cams. i have to disagree with whomever it was that said you must run a vacuum secondary carb on the street. ive been running mechanical carbs on street cars for 30 years and frankly think they are MORE streetable. of course you cant put a big double pumper on a stock engine and expect it to work. but on your engine a DP will work well on the street. especially with a stick trans.
Thanks for the p/n's. I'm deff. using a mech. secondary, especially with the stick...
i've always ran mech sec. and never had a problem, thanks again
 

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Just remember that mechanical cams and flat tappet cams the duration/lift numbers do not compute as equal because of lash. Cam companies do not stress that enough, I think because they assume builders realize the difference.
 

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Discussion Starter · #16 ·
xntrik said:
Just remember that mechanical cams and flat tappet cams the duration/lift numbers do not compute as equal because of lash. Cam companies do not stress that enough, I think because they assume builders realize the difference.
Yea, Thanks alot, I serously took a different look at my cam setup. If i went with what I wanted to go with be for i would have been in some trouble. Thanks again
 
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